Rolling of tubular blooms to produce tubes

ABSTRACT

According to the present disclosure there is provided a method and means for rolling tubular blooms to form tubes, in which at tubular bloom is passed during a plurality of working passes over a corresponding plurality of consecutive plugs arranged on a tension-loaded plug mandrel, said working passes being followed by a consecutive smoothing pass, wherein said working and smoothing passes are carried out in a continuous operation, in sequence, during which operation the external diameter of the tubular bloom is maintained substantially constant, the internal diameter of the bloom being enlarged during at least two of said working passes, and during said operation at least one smoothing pass being employed in the course of which an enlargement of the internal diameter takes place.

United States Patent [191 Vom Dorp et a].

[ ROLLING OF TUBULAR BLOOMS TO PRODUCE TUBES [75] Inventors: Walter Vom Dorp, Rheydt;- Hans Eversberg, Monchengladbach, both of Germany [73] Assignee: Wean United, lnc., Pittsburgh, Pa.

[22] Filed: Sept. 6, 1973 [21] Appl. N0.: 394,910

[52] US. Cl. 72/209, 72/370 [51] Int. Cl B2lb 17/10 [58] Field of Search 72/209, 234, 235, 370

[56] References Cited UNITED STATES PATENTS 3] 1,477 2/1885 Fisher et al. 72/209 424,213 3/1890 Kellogg 72/209 in] 3,823,594 Jul 16, 1974 Primary ExaminerMilton S. Mehr Attorney, Agent, or Firm-Henry C. Westin; Daniel Patch 5 7 ABSTRACT According to the present disclosure there is provided a method and means for rolling tubular blooms to form tubes, in which at tubular bloom is passed during a plurality of working passes over a corresponding pluraiity of consecutive plugs arranged on a tensionloaded plug mandrel, said working passes being followed by a consecutive smoothing pass, wherein said working and smoothing passes are carried out in a continuous operation, in sequence, during which operation the external diameter of the tubular bloom is maintained substantially constant, the internal diameter of the bloom being enlarged during at least two of said working passes, and during said operation at least one smoothing pass being employed in the course of which an enlargement of the internal diameter takes place.

6 Claims, 4 Drawing Figures PAIENTED JUL 1 s 1924 SHEET 1 BF 2 \lm QM mm Wm mac gm w w m J I J. J. Nam N m m V ozfipji v .N o 7 i B m h. w JL MM m on m EPAIENTEBMI elm sum 2 or z ROLLING OF TUBULAR BLOOMS TO PRODUCE TUBES The present invention relates to the rolling of tubular blooms to form tubes.

Even a small reduction in internal diameter is a disadvantage when using tubular blooms which have not yet been sufficiently worked, i.e. which have only experienced a small amount of deformation. Tubular blooms of this kind, which have only been worked to a minor extent and may still exhibit a casting type of structure, occur for example as products from continuous casting operations. During the first stage of working, these blooms are particularly susceptible to wrinkling and longitudinal cracking at the internal wall. These features can be rolled over, but not eradicated, during a smoothing phase in a separate skew-rolling operation over an internal tool.

It is an object of the present invention to overcome these disadvantages.

According to the present invention there is provided a method of rolling tubular blooms to form tubes, in which a tubular bloom is passed during a plurality of working passes over a corresponding plurality of consecutive plugs or tools arranged on a tension-loaded plug mandrel, said working passes being followed by a consecutive smoothing pass, wherein said working and smoothing passes are carried out in a continuous operation, in sequence, during which operation the external diameter of the tubular bloom is maintained substantially constant, the internal diameter of the bloom being enlarged during at least two of said working passes, and during said operation at least one smoothing pass being employed in the course of which an en-' largement of the internal diameter takes place.

In this fashion, the result is achieved that the reduction in wall thickness is produced by expansion from inside, ensuring that little wrinkling and cracking can occur in the internal wall. Finally, by the technique of direct smoothing in one sequence, while maintaining the internal pressure, it is ensured that an excellent smoothing effect is obtained at both external and internal surfaces.

The continuous mode of operation can advantageously be extended to include a sizing rolling operation in succession to the initial rolling and smoothing.

The invention can advantageously be contrived so that between the working passes and the smoothing pass, there is at least one intermediate pass which involves a lesser degree of deformation than is produced by the working passes and a greater degree of deformation than is produced by the smoothing pass. The intermediate pass here not only takes care of a certain part of the work of deformation but also acts as a preparation for the ensuing smoothing pass.

The present invention also provides a plurality of consecutive grooved rolls which cooperate with a corresponding number of plugs of differing diameters arranged upon a common plug mandrel, wherein the pass sections of all the groove rolls are the same, and wherein the diameters of the plugs increase from one to the next from one end of said common mandrel.

A considerable practical advantage resides in the fact that by stepping the plug diameters, adaptation to the working conditions required by different qualities of materials is made possible, and in this context it is merely necessary to exchange the plug mandrel for a corresponding different mandrel. The invention also makes it possible, for example, to design the first working pass to produce a relatively small deformation in order to be able to subject continuously cast tubular blooms first of all to an initial stabilizing rolling operation, whereafter, in the ensuing one or two or more additional roll stands, the main work of deformation is carried out.

The present invention will now be explained by way of example and with reference to the drawings, in which:

FIG. 1 is a graph showing the deformation which may be produced in a tubular bloom in the individual roll stands of a rolling mill in accordance withtwo possible procedures in a method of rolling tubes in accordance with the presentinvention; I

FIG. 2 schematically illustrates four roll stands each rotated through 90 from its normal position, which in use are arranged one behind the other, in a tube rolling mill in accordance with the present invention;

FIG. 3 illustrates a'plug mandrel for use in conjunction with the stands shown in FIG. 2; and

FIG. 4 illustrates a part of a continuous rolling mill in accordance with the present invention.

The graph shown in FIG. 1 illustrates the amounts of deformation'which may be produced in accordance with two operational procedures in a method in accordance with the invention. In the operational procedure corresponding to the full line plot the first working pass, a deformation of 25 percent is produced, during the second working pass a deformation of about 18 to 25 percent is produced, in a third intermediate pass the deformation is 13 to 15 percent, and during the last pass which as a result of the very small deformation produced constitutes a smoothing pass the deformation is about 5 to 7.5 percent. The smoothing operation may also effect a rounding operation, if desirable. In the procedure corresponding to the broken-line .plot, which is particularly suitable for continuously cast blooms, a deformation of only about 17.5 percent is produced in the first pass, a deformation of 25 percent in the second and in the third a deformation of 17.5 percent again, this being followed by the smoothing pass with a deformation of 10 percent.

FIGS. 2 and 3 should be taken in conjunction because they illustrate the relationship of the plugs to the roll pass sections. An arrow 8 indicates the direction of rolling. The plug mandrel 3 shown in FIG. 3, considered in the direction of rolling 8, carries four plugs 34, 35, 36, 37. The diameter d of the plug 37 is greater than the diameter d of the plug 36, the latter in turn greater than the diameter d of the plug 35 and the diameter d is greater than the diameter d, of the plug 34. The rolls 4, 5, 6 and 7 all have the same pass section diameter, symbolically indicated by the arrow marking the pass section radius. The plug mandrel 3 is equipped at one end with anchor means 9 for engagement with the lock (not shown) of the plug mandrel retainer mechanism.

The tube rolling mill illustrated in FIG. 4, exhibits four roll stands 40, 50, 60, with the corresponding drive arrangements 41, 51, 61, 71. The grooved rolls of FIG. 2, one of which is present in each of the stands 40, 50, 60, 70 have been omitted from the illustration for the sake of clarity. The plug mandrel 3 carries four plugs of which only the first 34 and the last 37 have been referenced. indicates a lock associated with the plug mandrel retainer mechanism and responsible for holding the plug mandrel in position in a tensionloaded operating condition. 11 indicates the conveyor devices for plug mandrel recirculation and broken-line arrows l2 assist the reader to see somewhat more clearly how recirculation takes place.

The continuous piercing mill can be followed by a sizing mill 30.

In accordance with the provisions of the patent statutes, we have explained the principle and operation of our invention and have illustrated and described what we consider to represent the best embodiment thereof.

We claim:

1. A method of rolling tubular blooms to form tubes, comprising the steps of passing a tubular bloom during a plurality of working passes over a corresponding plurality of consecutive plugs arranged on a tensionloaded plug mandrel, said working passes are followed by a consecutive smoothing pass, wherein said working and smoothing passes are carried out in a continuous operation, in sequence, during which operation the external diameter of the tubular bloom is maintained substantially constant while the internal diameter of the bloom is enlarged during at least two of said working passes. and during said operation at least one smoothing pass is employed in the course of which an enlargement of the internal diameter takes place.

2. A method as claimed in claim 1 wherein following said continuous operation a sizing rolling operation is effected in the same sequence.

3. A method as claimed in claim 1 wherein between a working pass and the smoothing pass, at least one intermediate pass is provided which produces a smaller degree of deformation than said working pass and a larger degree of deformation than said smoothing pass.

4. A method as claimed in claim 1 wherein said continuous operation comprises a first working pass producing a cross-sectional reduction of about 25 percent, a second working pass producing a cross-sectional reduction of about 25 percent, an intermediate pass producing a cross-sectional reduction of about 15 percent and a smoothing pass producing a cross-sectional reduction of about 5 percent.

5. A method as claimed in claim 1 wherein the continuous operation comprises a first working pass which produces a deformation of about 25 percent, a second working pass which produces a deformation of about 18 percent, an intermediate pass which produces a deformation of about 13 percent and a smoothing pass which produces a deformation of about 7.5 percent.

6. A method as claimed in claim 1 wherein the continuous operation comprises a first working pass which produces a deformation of about 17.5 percent, a second working pass which produces a deformation of about 25 percent, a third working pass which produces a deformation of about 17.5 percent and a smoothing pass which produces a deformation of about 10 per- UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 5,8215% Dated J y 9, 1974 I h Walter Vom Dor'p et a1.

It is certified that error appears in the abov eidentified patent and that said Letters Patent are hereby corrected as shown below:

On The Title Page, the following should be included:

[3% Fofeign Application Priority Data Dec. 1, 1972 West Germany P 22 59 657.2

Signed and sealed this 17th day of December 1974.

(SEAL) Attest:

I'icCOY M. GIBSON JR. C. MARSHALL-DAIIN Attesting Officer Commissioner of Patents IORM (10.69) USCOMM-DC 60376-P69 U-S. GOVIRNMENY PRINTING OFFICE! 869 o 

1. A method of rolling tubular blooms to form tubes, comprising the steps of passing a tubular bloom during a plurality of working passes over a corresponding plurality of consecutive plugs arranged on a tension-loaded plug mandrel, said working passes are followed by a consecutive smoothing pass, wherein said working and smoothing passes are carried out in a continuous operation, in sequence, during which operation the external diameter of the tubular bloom is maintained substantially constant while the internal diameter of the bloom is enlarged during at least two of said working passes, and during said operation at least one smoothing pass is employed in the course of which an enlargement of the internal diameter takes place.
 2. A method as claimed in claim 1 wherein following said continuous operation a sizing rolling operation is effected in the same sequence.
 3. A method as claimed in claim 1 wherein between a working pass and the smoothing pass, at least one intermediate pass is provided which produces a smaller degree of deformation than said working pass and a larger degree of deformation than said smoothing pass.
 4. A method as claimed in claim 1 wherein said continuous operation comprises a first working pass producing a cross-sectional reduction of about 25 percent, a second working pass producing a cross-sectional reduction of about 25 percent, an intermediate pass producing a cross-sectional reduction of about 15 percent and a smoothing pass producing a cross-sectional reduction of about 5 percent.
 5. A method as claimed in claim 1 wherein the continuous operation comprises a first working pass which produces a deformation of about 25 percent, a second working pass which produces a deformation of about 18 percent, an intermediate pass which produces a deformation of about 13 percent and a smoothing pass which produces a deformation of about 7.5 percent.
 6. A method as claimed in claim 1 wherein the continuous operation comprises a first working pass which produces a deformation of about 17.5 percent, a second working pass which produces a deformation of about 25 percent, a third working pass which produces a deformation of about 17.5 percent and a smoothing pass which produces a deformation of about 10 percent. 